This invention relates generally to valve operating mechanisms for use in internal combustion engines and, more particularly, to an oscillating rocker arm assembly with rolling members and to a method of assembly therefor.
Typically, a rocker arm assembly with rolling members is supported on a support shaft mounted perpendicularly on a support stud extending from the head of the engine. The rocker arm is pivoted on the support shaft, which serves as an inner raceway, by means of drawn cup needle roller bearings mounted on the rocker arm. If desired, a bearing sleeve may be mounted on the support shaft to provide the inner raceway, permitting use of a non-cylindrical support arm and facilitating the use of powder metal forming.
Axial retention of needle roller bearings of rocker arm assemblies is of critical importance. Inadequate axial retention of the needle roller bearings could result in the bearing cup "walking" out of the bore of the rocker arm, possibly causing catastrophic failure of the engine.
To provide axial retention of needle roller bearings on the rocker arm, two approaches have been used. In some rocker arm assemblies, a split ring engages a groove in each end of the support shaft to prevent axial movement of the needle roller bearings, i.e., movement axially outward with respect to the support shaft. Such retention requires the step of machining a groove in each end of the support shaft and the step of applying the split rings over the support shaft, both adding to the cost of the rocker arm assembly.
Alternatively, or in combination with the use of split rings over the ends of the support shaft, the needle roller bearings may be axially retained by a press fit within a bore of the rocker arm. In order to provide the required dimensional interference between the cup of the needle roller bearings and the rocker arm, the bore of the rocker arm must be accurately machined to tight tolerances with respect to the cups of the needle roller bearings, adding considerable cost to the rocker arm assembly.
The foregoing illustrates limitations known to exist in present rocker arm assemblies. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.